# Define here the models for your spider middleware
#
# See documentation in:
# https://docs.scrapy.org/en/latest/topics/spider-middleware.html

from scrapy import signals

# useful for handling different item types with a single interface
from itemadapter import is_item, ItemAdapter
from scrapy.http import HtmlResponse
from selenium.webdriver.common.by import By
from selenium.webdriver.support.wait import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.common.exceptions import TimeoutException, NoSuchElementException
from scrapy.downloadermiddlewares.useragent import UserAgentMiddleware
from scrapy.downloadermiddlewares.httpproxy import HttpProxyMiddleware
from fake_useragent import UserAgent
import time

class ScrapyexerciseSpiderMiddleware:
    # Not all methods need to be defined. If a method is not defined,
    # scrapy acts as if the spider middleware does not modify the
    # passed objects.

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_spider_input(self, response, spider):
        # Called for each response that goes through the spider
        # middleware and into the spider.

        # Should return None or raise an exception.
        return None

    def process_spider_output(self, response, result, spider):
        # Called with the results returned from the Spider, after
        # it has processed the response.

        # Must return an iterable of Request, or item objects.
        for i in result:
            yield i

    def process_spider_exception(self, response, exception, spider):
        # Called when a spider or process_spider_input() method
        # (from other spider middleware) raises an exception.

        # Should return either None or an iterable of Request or item objects.
        pass

    def process_start_requests(self, start_requests, spider):
        # Called with the start requests of the spider, and works
        # similarly to the process_spider_output() method, except
        # that it doesn’t have a response associated.

        # Must return only requests (not items).
        for r in start_requests:
            yield r

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)

class ScrapyexerciseDownloaderMiddleware:
    # Not all methods need to be defined. If a method is not defined,
    # scrapy acts as if the downloader middleware does not modify the
    # passed objects.

    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        return s

    def process_request(self, request, spider):
        # Called for each request that goes through the downloader
        # middleware.

        # Must either:
        # - return None: continue processing this request
        # - or return a Response object
        # - or return a Request object
        # - or raise IgnoreRequest: process_exception() methods of
        #   installed downloader middleware will be called
        return None

    def process_response(self, request, response, spider):
        # Called with the response returned from the downloader.

        # Must either;
        # - return a Response object
        # - return a Request object
        # - or raise IgnoreRequest
        return response

    def process_exception(self, request, exception, spider):
        # Called when a download handler or a process_request()
        # (from other downloader middleware) raises an exception.

        # Must either:
        # - return None: continue processing this exception
        # - return a Response object: stops process_exception() chain
        # - return a Request object: stops process_exception() chain
        pass

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)

class ToutiaoDownloaderMiddleware:

    def process_request(self, request, spider):
        if spider.name == 'toutiao':
            try:
                # 设置页面完全加载的超时时间
                # spider.driver.set_page_load_timeout(10)
                # 设置隐性等待 最长等待5s
                # spider.driver.implicitly_wait(5)
                spider.driver.get(request.url)
                # 设置显式等待 最多等待5s
                wait = WebDriverWait(spider.driver, 5)
                # 等待新闻列表容器加载完成
                wait.until(EC.presence_of_element_located((By.XPATH,"//div[@class='feed-container']")))
                # 使用快照保存浏览记录
                spider.driver.save_screenshot("logshot.png")
                # 使用JS的scrollTo方法实现将页面下滚到中间
                spider.driver.execute_script('window.scrollTo(0, document.body.scrollHeight/2)')
                for i in range(2):
                    time.sleep(5)
                    # 使用JS的scrollTo方法实现将页面滚到最底端
                    spider.driver.execute_script('window.scrollTo(0, document.body.scrollHeight)')
                # 获取加载完成的页面代码
                origin_code = spider.driver.page_source
                # 将源代码构造成为一个response对象并返回
                res = HtmlResponse(url=request.url, encoding='utf8', body=origin_code, request=request)
                return res
            except TimeoutException:
                print("time out")
            except NoSuchElementException:
                print("no such element")

    def spider_opened(self, spider):
        spider.driver.quit()
        spider.logger.info('Spider opened: %s' % spider.name)

class CrawlerUserAgentMiddleware(UserAgentMiddleware):

    def __init__(self, user_agent):
        location = './fake_useragent.json'
        self.user_agent = UserAgent(verify_ssl=False, path=location)

    @classmethod
    def from_crawler(cls, crawler):
        location = './fake_useragent.json'
        return cls(
            user_agent=UserAgent(verify_ssl=False, path=location)
        )

    def process_request(self, request, spider):
        agent = self.user_agent.random
        request.headers['User-Agent'] = agent
        print(request.headers['User-Agent'])

class CrawlerProxyMiddleware(HttpProxyMiddleware):

    def __init__(self, auth_encoding='latin-1'):
        # 数据库实例
        pass

    def process_request(self, request, spider):
        try:
            # 数据库中随机取出代理
            request.meta['proxy'] = 'http://{proxy}'
        except Exception as e:
            pass
